Unsolved Paleo Mysteries Month #19 – Mesozoic Maritime Mammal Molars

An illustration showing two different reconstructions of an extinct mammal. One is an otter-like animal, and the other is a flying-squirrel-like glider.

Icthyoconodon jaworowskorum was a member of the volaticotherians, a group of eutriconodonts most famous for featuring the earliest known gliding mammal. Living during the Early Cretaceous of Morocco (~145-140 mya), it’s known only from a few isolated teeth.

Based on the measurements of the teeth it was probably one of the larger eutriconodonts, close in size to Jugulator. I can’t find any body size estimates, but it may have have a total length of around 50-60cm (20-24″).

Plenty of fossil mammals are known solely from teeth, but what’s most interesting about this one is that its remains were found in coastal marine deposits without any signs of degradation or transport damage by water currents. This indicates the animal probably died at sea very close to the location where it was preserved.

A few other eutriconodonts are now known to have been semi-aquatic, so Ichthyocondon might have been adapted to a similar lifestyle, making it one of the earliest known marine mammals. Another potential explanation is that it was a Volaticotherium-like glider that got blown out to sea.

As with many of this month’s paleontological mysteries, we need some more substantial fossil remains to know for sure. I’ve reconstructed it here as both main possibilities, as an otter-like semi-aquatic animal and as a patagium-bearing glider.

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